Cuttings bed detection

ABSTRACT

A system and method for detecting a cuttings bed that includes a drill bit, a drillstring and a cuttings bed detector. The cuttings bed detector is positioned uphole of the drill bit. The method includes the steps of positioning a drill bit downhole, and positioning a cuttings bed detector uphole of the drill bit.

FIELD OF THE INVENTION

The present invention relates in general to wellbore drilling operations.

BACKGROUND

In conventional drilling operations, mud or other drilling fluid is pumped down a hollow bore in the drill string and is ejected from the drill bit to lift the drill cuttings out of the bore-hole.

In an inclined well-bore, at a certain deviation or sail angle, some of the drill cuttings being transported back to the surface by the drilling fluid fall out of the main flow and settle on the lower portion of the bore-hole forming a cuttings bed. These cuttings interfere with the drilling process and with the rotation of the rotating drill-pipe which also lies on the low side of the bore-hole. The cuttings bed may also jam up against the bottomhole assembly of the drillstring, leading to stuck pipe and potentially significant lost time and hole damage.

Therefore, it is a desire to provide an apparatus or method to alleviate the problem associated with cuttings beds.

SUMMARY

In view of the foregoing, and other considerations, the present invention relates to detecting cuttings bed in a downhole environment.

Accordingly, systems and methods for detecting a cuttings bed are disclosed. In one example, a system for detecting includes a drill bit and a drillstring. The drillstring includes a cuttings bed detector to detect the cuttings bed. The cuttings bed detector is positioned uphole of the drill bit.

In another example, a system for detecting a cuttings bed includes a section of casing with a cuttings bed detector.

In another example, a system for detecting a cuttings bed includes a section of casing with an ultrasonic source, a drillstring with an ultrasonic receiver, and a cuttings bed detector that includes the ultrasonic source and the ultrasonic receiver.

In another example, a method for detecting a cuttings bed includes the steps of positioning a drill bit downhole, and positioning a cuttings bed detector uphole of the drill bit.

The foregoing has outlined some of the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the present invention will be best understood with reference to the following detailed description of a specific example, when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial cross-section view of a system for detecting cuttings beds using a drillstring mounted cuttings bed detector.

FIG. 2A is an example of the system using a shallow nuclear density measurement sensor.

FIG. 2B is an example of the system of FIG. 1, using an ultrasonic sensor.

FIG. 2C is an example of the system using a low frequency pulse echo sensor.

FIG. 2D is an example of the system of FIG. 1, using an acoustic attenuation sensor.

FIG. 2E is an example of the system using a pressure transducer array.

FIG. 2F shows another example of the system shown in FIG. 1, using a mechanical sensor.

FIG. 3 is a partial cross-section drawing of another example of a system for detecting cuttings beds, using a casing mounted cuttings bed detector.

FIG. 4 is a partial cross-section drawing of another example of a system for detecting cuttings beds, using a casing mounted source and drillstring mounted receiver.

DETAILED DESCRIPTION

Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.

As used herein, the terms “up” and “down”; “upper” and “lower”; “uphole” and “downhole”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms “up,” “upper,” “uphole,” and other like terms are meant to indicate a position that is closer to the surface along the linear distance of the borehole. It is noted that through the use of directional drilling, a wellbore may not extend straight up and down. Thus, these terms describe relative positions along with the wellbore.

FIG. 1 is a partial cross section view of an example of a cuttings bed detection system, indicated generally by the numeral 10, illustrated in a deviated hole formed in earth formation 12. System 10 includes a drillstring 14 positioned within a borehole 16. Drillstring 14 includes bottomhole assembly 26, which typically includes measurement devices, such as MWD and LWD devices, as well as other downhole tools, such as mud motors and rotary steerable systems. Example borehole 16 is illustrated having a non-deviated casing section 18, deviated casing section 20 and an open horizontal section 22.

As drillstring 14 advances through borehole 16, the drill bit 28 drills the formations and generated drill cuttings that must be removed. The mud flow through the drill bit serves to cool and lubricate the drill bit, and to remove the drill cutting and carry them to the surface in the mud flow through the annulus between the drill string and the borehole wall. Cuttings may fall out of the mud flow and settle in a location in the borehole 16. Typically, cuttings bed 24 forms at locations such as where the mud flow fluid velocity drops below the level required to carry the cuttings produced by the drill bit, or in places where the fluid velocity is suddenly reduced. For example, cuttings bed 24 may be formed at casing points where the hole size increases, as well as where the flow area in the annulus increases because of a reduction in the diameter of the drill string, such as at the top of the bottomhole assembly 26. In addition, borehole angles close to the angle of repose for cuttings may be more likely to cause the formation of cuttings bed 24 due to avalanching, such as a borehole with an angle of about 60 degrees.

As will be described in more detail later, a cuttings bed detector may be located on the drill string, or it may be located in a casing or other equipment installed in a borehole. In one example, data from detector located in the drill string is transmitted to surface device via a wired drill pipe system. In another example, data from a detector located in the casing may be transmitted to the surface device via a wired casing structure. In some examples data may be collected by a sensor in one of the drill string or the casing, and then transmitted to a receiver in the other for retransmission to the surface. For example, a cuttings bed detector may be located in a casing and it may transmit data to a receiver in a drill string, and the data may be retransmitted to the surface via a wired drill pipe structure. In another example, a sensor may be mounted in a drill string and the data may be transmitted to a receiver located in a casing structure and then retransmitted to the surface through a wired casing structure.

Cuttings bed detectors are any device that may detect the presence of a cuttings bed in the wellbore or that may determine an increased likelihood of a cuttings bed based on measurements. Examples of such devices include shallow nuclear density measurement, ultrasonic measurement, low-frequency pulse echo, acoustic attenuation measurement, pressure transducer array, and mechanical detection. Specific examples of cuttings bed detectors will be described later.

In the example shown in FIG. 1, system 10 includes cuttings bed detector 30 located in or mounted on drillstring 14, e.g., mounted on a sub. As shown in FIG. 1, detector 30 is positioned at a location that is relatively far from the drill bit 28. A cuttings bed detector 30 may be positioned near the top of the BHA 26, or it may be positioned in the drill string above the BHA 26. For example, cuttings bed detector 30 may be positioned above bottomhole assembly 26 or where there is a substantial change in the diameter of bottomhole assembly 26. Detector 30 detects or locates cuttings bed 24.

System 10 also includes cuttings bed remover 40 mounted on drillstring 14. A cuttings bed remover is any device that is able to remove or reduce a cuttings bed. In one example, a drilling team or surface device 32 may control remover 40 via system 34, or other telemetry devices. In another example, cuttings bed detector 30 may communicate directly with remover 40, activating remover 40 upon detecting cuttings bed 24. In this manner, remover 40 may be combined with any of the disclosed cuttings bed detection systems to provide a closed loop control system without the need for telemetry to the surface.

In one example, cuttings bed remover 40 includes retractable impellors 41. Retractable impellors 41 may include vanes that are pushed out from the tool body into the annulus to move the cuttings. Remover 40 may include an electrical actuator that is initially configured so that the differential pressure between the interior and exterior of remover 40 keeps the vanes retracted. Motivating the actuator flips the differential pressure to move the vanes outside of remover 40. In another example of remover 40, drillstring 14 includes fixed impellors 43 distributed along the length of drill string 14 or at changes in the drillstring diameter, e.g., above the collars.

In another example, cuttings bed remover 40 may disperse cuttings bed 24 using fluid jetting. Drillstring 14 may include one or more valves 45. When positioned in the region of cuttings bed 24, valve 45 may be opened to release fluid to disturb the cuttings. Typically, this action would be combined with increasing the total mud flow rate so that the flow through bit 28 remains constant. The fluid flow may be pulsed and oriented, e.g., circumferentially to move cuttings at the bottom side of the hole, or upwards to move the cuttings up the hole. In another example, remover 40 may include a fluid by-pass valve to allow the system pressure drop to be maintained while increasing the carrying capacity of the annular fluid through increased velocity. With increased fluid flow, the valve need not necessarily be positioned proximate to cuttings bed 24.

In one example of cuttings bed detection system 10, shown in FIG. 2A, cuttings bed detector 30 a includes a shallow nuclear density sensor. In this example, detector 30 a includes a source of gamma-rays 42, at least one gamma-ray detector 44 and shielding 46 between the detector 44 and the source 42, so that only scattered gamma-rays are detected. During operation, gamma-rays from the tool source 42 travel through borehole 16, into earth formation 12. The gamma-rays will be scattered by the electrons in formation 12 or borehole 16 and some of them will be scattered back to detector 30 a. Because the count rate of detected gamma-rays varies with formation density, the measurement of detector 30 a may be used to measure density close to the source as a function of azimuth. If no cuttings bed 24 is proximate to detector 30 a, the measured density will be the formation density for all azimuths. If a cuttings bed 24 is present, the density will be higher on the low side of borehole 16. In this example, detector 30 a is mounted with a separation or stand-off from formation 12 and at some distance above any stabilization or large joint. In another example, detector 30 a uses X-rays instead of gamma rays.

In another example, shown in FIG. 2B, cuttings bed detector 30 b takes ultrasonic measurements. In this example, detector 30 b includes an ultrasonic source 48 a and detector 48 b, which may be components of ultrasonic transducer 49, to generate high frequency sound waves and evaluate the echo which is received back by the detector 30 b. Detector 30 b calculates the time interval between sending the signal and receiving the echo to determine the distance to the hole wall of borehole 16 and the reflection coefficient. A reduced stand-off on the low side of borehole 16 indicates cuttings bed 24. If casing 20 is steel or a similar material, then the difference in reflection from casing 20 and cuttings bed 24 may be more pronounced.

In another example, shown in FIG. 2C, cuttings bed detector 30 c detects cuttings bed 24 using a low frequency pulse echo. In this example, detector 30 c includes a low frequency pressure wave source and sensor 50, e.g., seismic to sonic range. Detector 30 c generates low frequency pressure waves through the annulus fluid. When a cuttings bed 24 fills a significant portion of the annulus, cuttings bed 24 may act as a reflector to the low frequency pressure waves propagating in the annulus fluid. The amplitude of the reflection, detected by sensor 50, indicates the size of cuttings bed 24. In this manner, sensor 50 would not necessarily need to be proximate to cuttings bed 24 and detector 30 c may detect cuttings bed 24 further up borehole 16, for example.

In another example, shown in FIG. 2D, cuttings bed detector 30 d detects cuttings bed 24 using acoustic attenuation measurements. In this example, detector 30 d is an acoustic attenuation sensor that includes a seismic or sonic transmitter 52 and an array of receivers or transducers 54. The transmitter 52 may be located near the bottom of drillstring 14. The array of transducers 54 may be distributed along drillstring 14. A significant attenuation between transducers 54 may indicate a large cuttings bed 24. In addition, acoustic reflections may be detected to locate cuttings bed 24. Acoustic data may be processed by the components of drillstring 14 (e.g., detector 30), devices connected to drillstring 14 (e.g., MWD or LWD tools) or surface device 32 (e.g., data transmitted via system 34). The acoustic waveforms may be used analyzed to interpret the size, shape and properties of cuttings bed 24, e.g., by analyzing dispersion or other frequency dependent behavior.

In another example, shown in FIG. 2E, cuttings bed detector 30 e detects cuttings bed 24 using a pressure transducer array. In this example, drillstring 14 includes an array of pressure transducers 56 distributed along drillstring 14 at selected intervals, e.g., every 1000 ft. During operation, cuttings bed 24 may restrict the mud flow in the annulus. The resulting pressure drop is detected by the transducers 56 on either side of the bed 24, e.g., transducers 56 d and 56 e. The data may be transmitted by wired drill pipe system 34, acoustic signals, or similar methods.

In another example, shown in FIG. 2F, cuttings bed detector 30f detects cuttings bed 24 using mechanical detection. In this example, detector 30 is a mechanical sensor that includes feeler arms or vanes 58 to detect a reduction in hole diameter (e.g., a simple caliper) or detect bed 24 based on selected properties of bed 24 (e.g., feeler arms 58 include a small probe or plow that is selectively blocked when in contact with bed 24). In another example, a mechanical cuttings bed detector 30f includes cuttings bed remover 40. For example, when vane 58 detects a bed 24, it may deploy itself to disperse the bed 24.

FIG. 3 shows another example of the cuttings bed detection system 10 in which a section of casing includes one or more cuttings bed detectors 60 to detect cuttings bed 24. In this example, casing 20 includes detector 60 mounted on the low side of casing section 20. Detector 60 includes transmitter or source 62 and receiver 64. Drillstring 14 may include one or more radio receivers 70. Cuttings bed detector 60 may transmit data to surface device 32 via wired drill pipe system 34 or radio receiver 70. Bottomhole assembly 26 may include a radio receiver 70 to warn of potentially dangerous cuttings beds moving up ahead of the widest section of drillstring 14.

In one example of system 10 g, casing mounted cutting bed detector 60 detects cuttings bed 24 using ultrasonic measurements. In this example, source 62 includes an ultrasonic source and receiver 64 includes an ultrasonic sensor. In another example, detector 60 detects bed 24 using sonic measurements. In this example, source 62 includes a sonic source and receiver 64 includes a sonic sensor. The sonic source and sonic receiver may be positioned fairly close to each other, e.g., a few inches apart. Detector 60 measures the time of travel between source 62 and receiver 64. A fluid borne wave may be significantly slower with cuttings bed 24 present. In another example, detector 60 utilizes a low frequency pulse echo to detect cuttings bed 24.

FIG. 4 shows another example of the cuttings bed detection system 10 in which a section of casing includes a transmitter or source 66 and drillstring 14 includes a sensor or receiver 68. In one example, source 66 includes a ultrasonic source positioned within casing 20 and receiver 68 includes an ultrasonic receiver. Receiver 68 receives the ultrasonic signals from source 66. The amplitude of the transmitted ultrasonic signal may be determined by one or more components of system 10 h, e.g., surface device 32, receiver 68, etc. Variations in transmitted amplitude may indicate the presence of cuttings bed 24.

In the examples shown in FIGS. 2F-4, system 34 includes casings 20 and 18 which each include communication lines 36 and transducers 38. Casings 20 and 18 are communicatively connected to each other, as well as surface device 32 (such as a computer system, receiver or similar instrument) and drillstring 14, via communication lines 36 and/or transducers 38. As a result, data received by one casing section in system 34 may be relayed via another casing section in system 34 to devices further uphole or downhole. For example, system 34 may relay data from detector 30 to surface device 32. This telemetry allows a drilling team to receive data concerning cuttings beds 24 and take action with respect to various drilling parameters, such as reducing weight-on-bit to reduce penetration rate, increasing flow rate, and increasing pipe rotation rate, among other actions.

Alternatively, or in addition to wired casing system 34, system 10 may include a wired drill pipe system 72 to transmit or relay data from downhole to further uphole, such as surface device 32. For example, drillstring 14 may include several communicatively connected tubular members 74. In the examples shown in FIGS. 14, each tubular member 74 includes communications couplers 76 and communications line 78. Communications couplers 76 may include transducers, inductive coupler elements, or similar devices to allow data to be relayed from one tubular member 74 to the next via communication lines 78.

In another example, shown in FIGS. 1-4, drillstring 14 may also include drillstring sensor 80 and drillstring receiver 82. Casing 20 may also include casing sensor 84 and casing receiver 86. Drillstring sensor 80 may short-hop data to casing receiver 86 for transmission via wired casing system 34. Alternatively, casing sensor 84 may short-hop data to drillstring receiver 82 for transmission via wired drill pipe system 72.

From the foregoing detailed description, it should be apparent that a system and method for detecting cuttings beds that is novel has been disclosed. Although specific embodiments have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed examples without departing from the spirit and scope of the invention as defined by the appended claims which follow. 

1. A system for detecting a cuttings bed, the system comprising: a drill string; a drill bit disposed at a lower end of the drill string; and a cuttings bed detector attached to the drill string.
 2. The system of claim 1, further comprising: a cuttings bed remover attached to the drill string.
 3. The system of claim 2, wherein the cuttings bed detector is operatively coupled to the cuttings bed remover, and configured to transmit a signal indicative of a detection of a cuttings bed.
 4. The system of claim 2, wherein the drill string comprises a wired drill pipe, and wherein the cuttings bed detector and the cuttings bed remover are operatively connected to the wired drill string.
 5. The system of claim 3, wherein the cuttings bed detector comprises an ultrasonic source and ultrasonic sensor.
 6. The system of claim 3, wherein the cuttings bed detector comprises a low frequency pressure wave source and low pressure wave sensor.
 7. The system of claim 3, wherein the cuttings bed detector comprises an acoustic attenuation sensor.
 8. The system of claim 3, wherein the cuttings bed detector comprises a pressure transducer array.
 9. The system of claim 3, wherein the cuttings bed detector comprises a mechanical sensor.
 10. A system for detecting a cuttings bed, the system comprising a section of casing having a cuttings bed detector.
 11. The system of claim 10, further comprising: a drillstring; and a cuttings bed remover positioned on the drillstring.
 12. The system of claim 11, further comprising a wired casing system.
 13. The system of claim 12, wherein the cuttings bed detector comprises an ultrasonic sensor.
 14. The system of claim 12, wherein the cuttings bed detector comprises a sonic sensor.
 15. The system of claim 12, wherein the cuttings bed detector comprises a low frequency pulse echo sensor.
 16. A system for detecting a cuttings bed, the system comprising: a section of casing comprising an ultrasonic source; a drillstring comprising an ultrasonic receiver; and a cuttings bed detector comprising the ultrasonic source and the ultrasonic receiver.
 17. The system of claim 16, further comprising a cuttings bed remover positioned on the drillstring.
 18. The system of claim 17, further comprising a wired drill pipe system.
 19. A method for detecting a cuttings bed, the method comprising the steps of: positioning a drill bit downhole; and positioning a cuttings bed detector uphole of the drill bit.
 20. The method of claim 19, further comprising the step of activating a cuttings bed remover upon detecting the cuttings bed. 